Citrus fruit trees are different from the deciduous fruit trees in winter, except for the roots of the rootstock. The lifespan of citrus leaves is usually 2 to 3 years. If the leaves are abnormally deciduous in winter (more than 20%), the tree potential and yield will be seriously affected.
The important role of citrus leaves
1 Perform photosynthesis to provide nutrients for the tree. Although the photosynthetic energy efficiency of citrus is not particularly high, citrus is resistant to negative, and the leaves have a high utilization rate of diffused light and weak light.
2 is the main driving force for citrus water and mineral nutrient absorption and transportation, while also reducing leaf temperature.
3 Citrus leaves are important organs for storing organic nutrients in the tree. The leaves store more than 40% of the total nitrogen and a large amount of carbohydrates.
4 When the citrus leaves are normal aging, some of the nutrients will return to the tree before the leaves. However, due to improper pests, freezing damage, cold damage or cultivation management measures, the leaves are abnormally detached, and the nutrients in the leaves are not refluxed, which will cause a large loss of nutrients.
The harm of citrus abnormal leaves
Abnormal leaves are extremely harmful to citrus fruit trees. The loss of organic nutrients not only affects the normal growth and flowering of citrus, but also causes plant death in severe cases.
Deciduous leaves appear before flower bud differentiation: the amount of flowers in the next year is reduced, even without flowers, and the spring shoots are more and more delicate.
After the completion of flower bud differentiation, the deciduous leaves are more flowers and poor in flower quality, most of which are leafless flowers, with low fruit setting rate and weakened tree.
Causes of abnormal defoliation of citrus in winter
Strong winds: There are often wind damages in winter. Strong winds can cause mechanical damage to citrus trees, and there are a lot of leaves falling off and branches broken.
Low temperature: The temperature in winter is low. When the temperature is lower than the lowest temperature that citrus can tolerate for a long time, it will cause internal freezing, dehydration, defoliation of trees, freezing of branches, and even death of trees.
Drought: There is less rain in winter and the climate is drier. When the soil is dry, the root activity is weak, which restricts the absorption of water, destroys the normal water supply to the plant, and causes the leaves and tips to curl and wither due to water loss.
In winter, the temperature is low, the plant enzyme activity is reduced, the citrus roots have low ability to absorb water and fertilizer, the light is also less, the photosynthesis efficiency is low, and the photosynthetic nutrition is less.
However, the respiration of citrus is not reduced synchronously. The rate of photosynthetic nutrient consumption in the tree is greater than the speed at which photosynthetic nutrition is produced. If the organic nutrients stored in the tree are insufficient, the tree will rapidly weaken and the leaves turn yellow and fall. Reasons for the lack of organic nutrients in the tree include:
1 The amount of fruit is large, the number of functional leaves is small, and the production of organic nutrients is insufficient.
2 The tree is weak or vain, and the metabolism is disordered.
3 root or soil problems, nutritional supply barriers.
Disease and pest
The main diseases are Huanglongbing, anthracnose, macula maculopathy, nematode disease, brown rot of plague, brown spot disease and so on.
The main pests: red spider, rust tick, scale insects and so on.
One-time fruit picking: It is easy to lose a lot of nutrients. If the tree is not replenished in time, it will easily cause leaves.
Ring-cutting flowers: excessive ring cutting or improper ring cutting, slow wound healing, can cause photosynthesis products can not be transported to the roots for a long time, causing serious damage to the root system, especially the xylem, and also affect the transportation of mineral elements. The leaves are yellowed and the tree is weak, causing a lot of fallen leaves.
Orchard canopy: The growth of the leaves requires proper illumination. The tree shape is poor, and it is not trimmed all the year round. It will cause the canopy to be closed, the light is insufficient, and the inner stalk leaves become thinner or even yellower, causing the inner deciduous leaves.
Phytotoxicity: Stone sulphur mixture, pineine mixture, oil emulsion and other agents are used excessively, which is easy to cause defoliation; excessive concentration of fertilizer or application of unfertilized organic fertilizer leads to burning roots, causing a large number of citrus leaves.
Measures to prevent citrus winter leaves
Strengthen tree nutrition
Before and after fruit picking, the tree nutrient consumption is large. If it is not replenished in time, it will lead to severe defoliation in winter, affecting the normal differentiation of flower buds and the growth and development of spring shoots, leaves and flowers after differentiation.
For the moderate tree that has been hung, the winter fertilizer is applied in time.
For trees with weaker trees, a small amount of compound fertilizer can be applied one week before harvesting, and then the winter fertilizer is taken before the dormant period.
For trees that keep trees fresh, the organic liquid fertilizer should be applied to the fruit trees in mid-December to supplement the nutrients consumed by the fruits hanging on the trees for a long time, in order to restore the tree potential.
Pay attention to cold and warm
In winter, the temperature is low, and the citrus is susceptible to cold damage and freezing damage. Especially the trees with winter shoots are more susceptible to freezing. After freezing, it will cause the leaves of the tree, the freezing of the branches, and even the death of the tree.
Specifically, it can be used to prevent cold by cultivating soil, laminating, and spraying high-purity phosphorus potassium source pool before freezing. Special reminders for fruit farmers should always pay attention to the weather and prevent it early.
Prevention and control of pests and diseases
Red spider, anthracnose, and maculopathy are important reasons for causing a large number of deciduous winter and spring leaves in citrus.
For the defoliation caused by nematode disease, pay attention to the application of sea snail bio-stimulant (root type) after medication to help restore root activity.
In particular, it is more common for Huanglongbing trees to have a large number of fallen leaves in winter. Once found, don't have a chance to be lucky.
For the identification and treatment of Huanglong disease, please refer to: "Please correctly understand Huanglong disease."
Standardizing farming operations
Rational use of fertilizer to avoid phytotoxicity and fat damage.
Drought not only affects the vitality and absorption of roots, but also easily induces red spiders.
If the leaves are caused by circumcision, the ring cuttings should be topdressed and the wounds should be wrapped with green film or electrical tape to facilitate healing.
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